On average, he was the first defenseman selected in Yahoo! leagues (19th overall pick) this season. Even with such lofty expectations surrounding him, the offensive-minded blueliner managed to fully satisfy his fantasy owners through 13 games of good health.

But all that changed Wednesday when the Ottawa Senators' defenseman lacerated his left Achilles tendon against the Pittsburgh Penguins. The injury will require surgery to repair, and he's out indefinitely.

In losing Karlsson for what is expected to be an extended period of time, fantasy owners will be without the production of the NHL's current shot on goal leader (63), as well as one of only seven blueliners in the League with 10-plus points.

Owners in keeper leagues certainly should retain Karlsson, because if he fully recovers, the sky remains the limit for the young defenseman. Even in shallow leagues, it's important to wait until he has surgery and a recovery time is announced before parting ways with a player you likely selected in the first or second round of your draft.